A spool is a component used to collect various films, tapes or papers and other soft and long material. In the process of winding the material by the spool, a few initial laps of the material are often dented by the end of the material, resulting in creases on the material. In the fields of optical films and the like which have high requirements for surface material, the material is often discarded.
To overcome the above problems, a spool is disclosed by the applicant in a Chinese utility model patent with a filing date of Mar. 21, 2011 and an application number of CN201120074757.7. The spool includes a tube used to wind material to be wound. A groove is formed in an outer surface of the tube. The groove has a vertical surface, and a bottom surface of the groove is in smooth connection with the outer surface of the tube.
In the above structure, the groove is formed so that no crease is generated in a few initial wound laps of the material to be wound. However, in practical use, due to the unevenness of the end part of the material, the end part of the material cannot be smoothly intertwined with the groove. Thus, there are still defects of dents caused by a gap between the end part and the groove in the winding process, which need to be improved.